German Patent Application DE 199 62 241 A1 describes a mechanical-electronic position sensor including an angle transducer in the form of a toothed gearing, a magnetic pulse encoder driven by said toothed gearing, an analog-to-digital converter (hereinafter called “A/D converter”), a microprocessor and an output stage having an output signal which may be analog or digital, as desired.
A mechanical-electronic position switch is known from German Utility Model DE 202 03 214 U1. An actuating plunger, a potentiometer, a microcontroller, and electronic switching contacts are disposed in a housing. The actuating plunger is coupled to the wiper of the potentiometer. Upon actuation of the plunger, a varying electrical signal is fed to the microcontroller, said signal causing a change of state of the switching contacts when it exceeds or falls below a programmed threshold value. The switching contacts are connected at their outputs to the connecting terminals. No information is given on how failures of the electronics can be detected to prevent erroneous output signals from leading to maloperations at the periphery of the position switch.
U.S. Pat. No. 5,426,776 A describes a watchdog circuit, which serves to monitor the execution of a program in a microprocessor. The watchdog circuit includes a voltage comparator whose input is connected to a charge storage device formed by a first resistor-capacitor series combination and whose output is connected to a reset input of the micropressor. A charge pump, which includes a second resistor-capacitor series combination and a first semiconductor valve connected to a supply potential, is connected to the charge storage device by a second semiconductor valve. During regular operation, a watchdog output of the microprocessor supplies a dynamically changing watchdog signal to the charge pump, which keeps the charge voltage of the charge storage device below a threshold value by regularly discharging the same. Upon interruption of the microprocessor, the dynamic changing of the watchdog signal, and thus, the discharging of the charge storage device by the charge pump ends, whereupon the charge voltage exceeds the threshold value, causing the comparator to output a reset signal.